Add "lineprocessor" sample program

samples/lineprocessor.cc

Index: samples/lineprocessor.cc
diff --git a/samples/lineprocessor.cc b/samples/lineprocessor.cc
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+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <v8.h>
+#include <v8-debug.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/**
+ * This sample program should demonstrate certain aspects of debugging
+ * standalone V8-based application.
+ *
+ * The program reads input stream, processes it line by line and print
+ * the result to output. The actual processing is done by custom JavaScript
+ * script. The script is specified with command line parameters.
+ *
+ * The main cycle of the program will sequentially read lines from standard
+ * input, process them and print to standard output until input closes.
+ * There are 2 possible configuration in regard to main cycle.
+ *
+ * 1. The main cycle is on C++ side. Program should be run with
+ * --main-cycle-in-cpp option. Script must declare a function named
+ * "ProcessLine". The main cycle in C++ reads lines and calls this function
+ * for processing every time. This is a sample script:
+
+function ProcessLine(input_line) {
+  return ">>>" + input_line + "<<<";
+}
+
+ *
+ * 2. The main cycle is in JavaScript. Program should be run with
+ * --main-cycle-in-js option. Script gets run one time at all and gets
+ * API of 2 global functions: "read_line" and "print". It should read input
+ * and print converted lines to output itself. This a sample script:
+
+while (true) {
+  var line = read_line();
+  if (!line) {
+    break;
+  }
+  var res = line + " | " + line;
+  print(res);
+}
+
+ *
+ * When run with "-p" argument, the program starts V8 Debugger Agent and
+ * allows remote debugger to attach and debug JavaScript code.
+ *
+ * Interesting aspects:
+ * 1. Wait for remote debugger to attach
+ * Normally the program compiles custom script and immediately runs it.
+ * If programmer needs to debug script from the very beginning, he should
+ * run this sample program with "--wait-for-connection" command line parameter.
+ * This way V8 will suspend on the first statement and wait for
+ * debugger to attach.
+ *
+ * 2. Unresponsive V8
+ * V8 Debugger Agent holds a connection with remote debugger, but it does
+ * respond only when V8 is running some script. In particular, when this program
+ * is waiting for input, all requests from debugger get deferred until V8
+ * is called again. See how "--callback" command-line parameter in this sample
+ * fixes this issue.
+ */
+
+enum MainCycleType {
+  CycleInCpp,
+  CycleInJs
+};
+
+const char* ToCString(const v8::String::Utf8Value& value);
+void ReportException(v8::TryCatch* handler);
+v8::Handle<v8::String> ReadFile(const char* name);
+v8::Handle<v8::String> ReadLine();
+
+v8::Handle<v8::Value> Print(const v8::Arguments& args);
+v8::Handle<v8::Value> ReadLine(const v8::Arguments& args);
+bool RunCppCycle(v8::Handle<v8::Script> script, v8::Local<v8::Context> context,
+                 bool report_exceptions);
+
+v8::Persistent<v8::Context> debug_message_context;
+
+
+void DispatchDebugMessages() {
+  // We are in some random thread. We should already have v8::Locker acquired
+  // (we requested this when registered this callback). We was called
+  // because new debug messages arrived; they may have already been processed,
+  // but we shouldn't worry about this.
+  //
+  // All we have to do is to set context and call ProcessDebugMessages.
+  //
+  // We should decide which V8 context to use here. This is important for
+  // "evaluate" command, because it must be executed some context.
+  // In our sample we have only one context, so there is nothing really to
+  // think about.
+  v8::Context::Scope scope(debug_message_context);
+
+  v8::Debug::ProcessDebugMessages();
+}
+
+
+int RunMain(int argc, char* argv[]) {
+  v8::V8::SetFlagsFromCommandLine(&argc, argv, true);
+  v8::HandleScope handle_scope;
+
+  v8::Handle<v8::String> script_source(NULL);
+  v8::Handle<v8::Value> script_name(NULL);
+  int script_param_counter = 0;
+
+  int port_number = -1;
+  bool wait_for_connection = false;
+  bool support_callback = true;
+  MainCycleType cycle_type = CycleInCpp;
+
+  for (int i = 1; i < argc; i++) {
+    const char* str = argv[i];
+    if (strcmp(str, "-f") == 0) {
+      // Ignore any -f flags for compatibility with the other stand-
+      // alone JavaScript engines.
+      continue;
+    } else if (strcmp(str, "--callback") == 0) {
+      // TODO(548): implement this.
+      printf("Error: debugger agent callback is not supported yet.\n");
+      return 1;
+    } else if (strcmp(str, "--wait-for-connection") == 0) {
+      wait_for_connection = true;
+    } else if (strcmp(str, "--main-cycle-in-cpp") == 0) {
+      cycle_type = CycleInCpp;
+    } else if (strcmp(str, "--main-cycle-in-js") == 0) {
+      cycle_type = CycleInJs;
+    } else if (strcmp(str, "-p") == 0 && i + 1 < argc) {
+      port_number = atoi(argv[i + 1]);
+      i++;
+    } else if (strncmp(str, "--", 2) == 0) {
+      printf("Warning: unknown flag %s.\nTry --help for options\n", str);
+    } else if (strcmp(str, "-e") == 0 && i + 1 < argc) {
+      script_source = v8::String::New(argv[i + 1]);
+      script_name = v8::String::New("unnamed");
+      i++;
+      script_param_counter++;
+    } else {
+      // Use argument as a name of file to load.
+      script_source = ReadFile(str);
+      script_name = v8::String::New(str);
+      if (script_source.IsEmpty()) {
+        printf("Error reading '%s'\n", str);
+        return 1;
+      }
+      script_param_counter++;
+    }
+  }
+
+  if (script_param_counter == 0) {
+    printf("Script is not specified\n");
+    return 1;
+  }
+  if (script_param_counter != 1) {
+    printf("Only one script may be specified\n");
+    return 1;
+  }
+
+  // Create a template for the global object.
+  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New();
+
+  // Bind the global 'print' function to the C++ Print callback.
+  global->Set(v8::String::New("print"), v8::FunctionTemplate::New(Print));
+
+  if (cycle_type == CycleInJs) {
+    // Bind the global 'read_line' function to the C++ Print callback.
+    global->Set(v8::String::New("read_line"),
+                v8::FunctionTemplate::New(ReadLine));
+  }
+
+  // Create a new execution environment containing the built-in
+  // functions
+  v8::Handle<v8::Context> context = v8::Context::New(NULL, global);
+  debug_message_context = v8::Persistent<v8::Context>::New(context);
+
+
+  // Enter the newly created execution environment.
+  v8::Context::Scope context_scope(context);
+
+  v8::Locker locker;
+
+  if (support_callback) {
+    v8::Debug::SetDebugMessageDispatchHandler(DispatchDebugMessages, true);
+  }
+
+  if (port_number != -1) {
+    const char* auto_break_param = "--debugger_auto_break";
+    v8::V8::SetFlagsFromString(auto_break_param, strlen(auto_break_param));
+    v8::Debug::EnableAgent("lineprocessor", port_number, wait_for_connection);
+  }
+
+  bool report_exceptions = true;
+
+  v8::Handle<v8::Script> script;
+  {
+    // Compile script in try/catch context.
+    v8::TryCatch try_catch;
+    script = v8::Script::Compile(script_source, script_name);
+    if (script.IsEmpty()) {
+      // Print errors that happened during compilation.
+      if (report_exceptions)
+        ReportException(&try_catch);
+      return 1;
+    }
+  }
+
+  {
+    v8::TryCatch try_catch;
+
+    script->Run();
+    if (try_catch.HasCaught()) {
+      if (report_exceptions)
+        ReportException(&try_catch);
+      return 1;
+    }
+  }
+
+  if (cycle_type == CycleInCpp) {
+    bool res = RunCppCycle(script, v8::Context::GetCurrent(),
+                           report_exceptions);
+    return !res;
+  } else {
+    // All is already done.
+  }
+  return 0;
+}
+
+
+bool RunCppCycle(v8::Handle<v8::Script> script, v8::Local<v8::Context> context,
+                 bool report_exceptions) {
+  v8::Locker lock;
+
+  v8::Handle<v8::String> fun_name = v8::String::New("ProcessLine");
+  v8::Handle<v8::Value> process_val =
+      v8::Context::GetCurrent()->Global()->Get(fun_name);
+
+  // If there is no Process function, or if it is not a function,
+  // bail out
+  if (!process_val->IsFunction()) {
+    printf("Error: Script does not declare 'ProcessLine' global function.\n");
+    return 1;
+  }
+
+  // It is a function; cast it to a Function
+  v8::Handle<v8::Function> process_fun =
+      v8::Handle<v8::Function>::Cast(process_val);
+
+
+  while (!feof(stdin)) {
+    v8::HandleScope handle_scope;
+
+    v8::Handle<v8::String> input_line = ReadLine();
+    if (input_line == v8::Undefined()) {
+      continue;
+    }
+
+    const int argc = 1;
+    v8::Handle<v8::Value> argv[argc] = { input_line };
+
+    v8::Handle<v8::Value> result;
+    {
+      v8::TryCatch try_catch;
+      result = process_fun->Call(v8::Context::GetCurrent()->Global(),
+                                 argc, argv);
+      if (try_catch.HasCaught()) {
+        if (report_exceptions)
+          ReportException(&try_catch);
+        return false;
+      }
+    }
+    v8::String::Utf8Value str(result);
+    const char* cstr = ToCString(str);
+    printf("%s\n", cstr);
+  }
+
+  return true;
+}
+
+int main(int argc, char* argv[]) {
+  int result = RunMain(argc, argv);
+  v8::V8::Dispose();
+  return result;
+}
+
+
+// Extracts a C string from a V8 Utf8Value.
+const char* ToCString(const v8::String::Utf8Value& value) {
+  return *value ? *value : "<string conversion failed>";
+}
+
+
+// Reads a file into a v8 string.
+v8::Handle<v8::String> ReadFile(const char* name) {
+  FILE* file = fopen(name, "rb");
+  if (file == NULL) return v8::Handle<v8::String>();
+
+  fseek(file, 0, SEEK_END);
+  int size = ftell(file);
+  rewind(file);
+
+  char* chars = new char[size + 1];
+  chars[size] = '\0';
+  for (int i = 0; i < size;) {
+    int read = fread(&chars[i], 1, size - i, file);
+    i += read;
+  }
+  fclose(file);
+  v8::Handle<v8::String> result = v8::String::New(chars, size);
+  delete[] chars;
+  return result;
+}
+
+
+void ReportException(v8::TryCatch* try_catch) {
+  v8::HandleScope handle_scope;
+  v8::String::Utf8Value exception(try_catch->Exception());
+  const char* exception_string = ToCString(exception);
+  v8::Handle<v8::Message> message = try_catch->Message();
+  if (message.IsEmpty()) {
+    // V8 didn't provide any extra information about this error; just
+    // print the exception.
+    printf("%s\n", exception_string);
+  } else {
+    // Print (filename):(line number): (message).
+    v8::String::Utf8Value filename(message->GetScriptResourceName());
+    const char* filename_string = ToCString(filename);
+    int linenum = message->GetLineNumber();
+    printf("%s:%i: %s\n", filename_string, linenum, exception_string);
+    // Print line of source code.
+    v8::String::Utf8Value sourceline(message->GetSourceLine());
+    const char* sourceline_string = ToCString(sourceline);
+    printf("%s\n", sourceline_string);
+    // Print wavy underline (GetUnderline is deprecated).
+    int start = message->GetStartColumn();
+    for (int i = 0; i < start; i++) {
+      printf(" ");
+    }
+    int end = message->GetEndColumn();
+    for (int i = start; i < end; i++) {
+      printf("^");
+    }
+    printf("\n");
+  }
+}
+
+
+// The callback that is invoked by v8 whenever the JavaScript 'print'
+// function is called.  Prints its arguments on stdout separated by
+// spaces and ending with a newline.
+v8::Handle<v8::Value> Print(const v8::Arguments& args) {
+  bool first = true;
+  for (int i = 0; i < args.Length(); i++) {
+    v8::HandleScope handle_scope;
+    if (first) {
+      first = false;
+    } else {
+      printf(" ");
+    }
+    v8::String::Utf8Value str(args[i]);
+    const char* cstr = ToCString(str);
+    printf("%s", cstr);
+  }
+  printf("\n");
+  fflush(stdout);
+  return v8::Undefined();
+}
+
+
+// The callback that is invoked by v8 whenever the JavaScript 'read_line'
+// function is called. Reads a string from standard input and returns.
+v8::Handle<v8::Value> ReadLine(const v8::Arguments& args) {
+  if (args.Length() > 0) {
+    return v8::ThrowException(v8::String::New("Unexpected arguments"));
+  }
+  return ReadLine();
+}
+
+v8::Handle<v8::String> ReadLine() {
+  const int buffer_size = 1024 + 1;
+  char buffer[buffer_size];
+
+  char* res;
+  {
+    v8::Unlocker unlocker;
+    res = fgets(buffer, buffer_size, stdin);
+  }
+  if (res == NULL) {
+    v8::Handle<v8::Primitive> t = v8::Undefined();
+    return reinterpret_cast<v8::Handle<v8::String>&>(t);
+  }
+  // remove newline char
+  for (char* pos = buffer; *pos != '\0'; pos++) {
+    if (*pos == '\n') {
+      *pos = '\0';
+      break;
+    }
+  }
+  return v8::String::New(buffer);
+}